1. Field
The present invention relates to a method of manufacturing a rigid-flexible printed circuit board and, more particularly, to a method of manufacturing a rigid-flexible printed circuit board including CL via holes which can facilitate electrical connection to an inner circuit pattern in a flexible region.
2. Description of the Related Art
Generally, a rigid-flexible printed circuit board is formed by structurally combining a rigid substrate, which is made of a rigid material, with a film type flexible substrate, which can be easily bent. In the rigid-flexible printed circuit board, the rigid substrate is connected with the flexible substrate without an additional connector.
To meet the recent trend toward miniaturized, light, and slim devices, electronic devices, such as mobile phones, Personal Digital Assistants (PDAs) and digital cameras, require design technology for optimizing the mounting space for electronic parts as well as fine processing technology for miniaturizing the electronic parts to be mounted. Particularly, it is required to provide a printed circuit board capable of mounting highly integrated electronic parts at high density.
FIGS. 1A to 1N are process diagrams showing a conventional method of manufacturing a rigid-flexible printed circuit board. The conventional method of manufacturing a rigid-flexible printed circuit board will be described with reference to FIGS. 1A to 1N below.
As shown in FIG. 1A, a double-sided Flexible Copper Clad Laminate (FCCL) 10 with an insulation layer 12 and copper foil layers 14 respectively formed on two sides of the insulation layer 12 is provided, and, as shown in FIG. 1B, predetermined inner circuit patterns 16 are respectively formed on the two sides of the insulation layer 12 using the copper foil layers 14.
As shown in FIG. 1C, before coverlays 20 are respectively layered on two sides of the double-sided FCCL 10, first windows 22 are respectively formed in the portions of coverlays 20 corresponding to a flexible region.
Then, as shown in FIG. 1D, a base substrate 30 is formed by respectively layering the coverlays 20, in which the first windows 22 are respectively formed, on the two sides of the double-sided FCCL 10 to conform to the inner circuit patterns (not shown) formed on the two sides of the double-sided FCCL 10.
As shown in FIG. 1E, since the portions of the copper foil layers 14 of the double-sided FCCL 10 corresponding to the first windows are open and are then etched through a subsequent etching process, resists 40 are formed to protect the open portions of the copper foil layers 14.
As shown in FIG. 1F, a rigid region is formed by respectively layering insulation layers 32 and 34 on two sides of the remainder of the base substrate 30 other than the portion of the base substrate 30 including the region in which the resists 40 are formed, and a laminated body 50 is formed by respectively layering copper foil layers 36 and 38, having the same size as the base substrate 30, on the insulation layers 32 and 34.
Here, the portion of the base substrate 30 including the resists 40 forms a flexible region.
As shown in FIG. 1G, a Plated Through Hole (PTH) 52 for connecting the upper copper foil layer 36 and lower copper foil layer 38 in the rigid region is formed using a drilling machine, and, as shown in FIG. 1H, a second window 54 is formed in the outermost copper foil layer 36 of the rigid region.
As shown in FIG. 1I, a blind via hole 56 is formed in the rigid region to correspond to the second window 54, and, as shown in FIG. 1J, a plating layer 60 is formed throughout the laminated body 50.
As shown in FIG. 1K, outer circuit patterns 70 are formed by partially removing the plating layer, additional resists 42 are formed to a predetermined thickness in order to remove the resists 40 formed in the first windows, and, as shown in FIG. 1L, the resists 40 and 42 are then removed.
As shown in FIG. 1M, solder resists 80 are formed on the outer circuit patterns 70 to expose portions of the outer circuit patterns, and, as shown in FIG. 1N, the rigid-flexible printed circuit board is completed by applying conductive paste 90 to form ground shield layers on the outer sides of the flexible region.
However, since, in the conventional rigid-flexible printed circuit board, the windows are formed in the coverlays through previous processing, there have been problems in that manufacturing cost is high, and the process of layering the coverlays on the double-sided FCCL in to conform to the inner circuit patterns respectively formed on the two sides of the double-sided FCCL is difficult, and thus the cost of performing the processing is high.
Further, there have been problems in that the cost of applying and removing the resists is high, and defects may occur because residual resist is present on the circuit pattern after removal of the resists.